Exhaust gases and particulates that are typically generated from internal combustion engines such as, for example, diesel engines, gasoline engines, and gaseous-fuel powered engines, generally need to be treated before entering the atmosphere to comply with emission standards. The engine exhaust for some engines, such as diesel engines, may include carbon monoxide, unburned hydrocarbons, and oxides of nitrogen (NOx) as well as particulates. As part of some treatment processes, the exhaust gases may pass through an aftertreatment system which may include selective catalytic reduction (SCR) to reduce NOx. As part of the SCR process, a reductant, such as urea or ammonia, is injected into the exhaust gas stream and adsorbed downstream onto an SCR catalyst or group of SCR catalysts. The SCR process converts NOx into diatomic nitrogen (N2) and water (H2O).
In particular, for an efficient SCR process, after the reductant is injected into the exhaust gas stream, the exhaust mass flow and reductant vapor should be distributed evenly across the SCR catalyst or group of SCR catalysts. While effective, some traditional vertical SCR designs, however, are challenged with distributing the exhaust mass flow and reductant vapor evenly across the SCR catalysts due to space requirements within the aftertreatment system. Moreover, such traditional vertical SCR designs are limited in providing a convenient aid to assist in assembling multiple stages of SCR catalysts.
U.S. Pat. No. 7,451,594 (the '594 patent) discloses an exhaust flow distribution device. The exhaust flow distribution device includes a concave plate having elongated distribution holes. The elongated distribution holes have a width that continuously increases as the hole extends from a central region outwardly to a peripheral edge. The '594 publication fails to disclose a distribution device that evenly distributes exhaust mass flow and reductant vapor onto catalysts and that aids in assembling multiple stages of catalysts.